I have both a 74 240 D manual and an 81 SD of course automatic. They are as different as an old Town canoe (240)
to a Yacht tender(SD). Someone told me that the 240D was designed as an European Taxi cab and then dolled up with sunroof and a few goodies for this country.The SD reminds me of what a Cadillac should have been a very forgiving wonderfully comfortable auto that just begs to be driven. Possibly I have a split personality as I love them both dearly.I Don't find the SD any harder to work on in some respects it's easier as there is more room in the engine compartment.